Every 100 years is called a century, made up of 10 decades.
bidecadal
True.
The phrase "once every 3 years" can be expressed as "triennial." This term refers to an event or occurrence that happens every three years. Alternatively, you could also say "every three years" for clarity.
An event occurring every ten years is called a "decennial" event. The term "decade" refers to a period of ten years, and thus, "decennial" signifies something that takes place once within that time frame. Examples include the decennial census conducted in various countries.
A false rumor is floating around the Internet that this happens only once every 823 years. The reality is that it happens whenever the first day of October is on Friday, which happens on average once every seven years. The last time for this "rare" event was 6 years ago, back in 2004. And the time before that was 5 years previously, in 1999.
An event occurring every two years is referred to as a biennial event. This pattern indicates that the event happens once every two years.
An event that occurs every thirty years is called a "triennial" event. However, this term can be misleading since "triennial" technically refers to something happening every three years. For events specifically occurring every thirty years, the term "tricenary" can be used, although it is less common.
A triennial event happens every three years.
Something that happens every six years is sexennial.
It is a triennial event. A triennial event happens three times a year.
bidecadal
nothing
Semicentennial
True.
I think you are asking about a census.
Leap year
Chicago Cubs in the World Series?